The present invention relates to a reservoir tank mounted to a master cylinder or a hydraulic booster of a vehicle brake system.
A typical conventional reservoir tank 10 is shown in FIG. 6B, which comprises a tank body 1 comprising a lower shell 1a and an upper shell 1b, which are joined together by melting their mating surfaces with a hot plate H (FIG. 6A), putting the top shell 1b onto the lower shell 1a so that their molten mating surfaces contact each other, and allowing the mating surfaces to harden so as to be fixed to each other.
The reservoir tank 10 includes partition walls 2 that divide the interior of the tank body 1 into a plurality of chambers, thereby minimizing pulsation of hydraulic fluid F in the tank body, a filter 4 provided in one of the chambers through which hydraulic fluid F flows into and out of the reservoir tank, and a float 5 and a fluid level sensor 6 provided in a fluid level detecting chamber 3. The flow of hydraulic fluid F into and out of the fluid level detecting chamber 3 is restricted by a partition plate 7. The upper shell 1b has a fluid supply port 8. (This particular type of reservoir tank 10 is disclosed in JP patent publication 11-20660.)
The fluid level sensor has a shaft 6a which carries at its top end a retainer 9 that restricts the movement of the float 5 and also prevents separation of the float 5 from the fluid level sensor 6. The retainer 9 is e.g. a snap ring fixed to the shaft of the sensor 6 by caulking or bonding.
In order to mount the retainer 9 to the shaft of the sensor 6, it is necessary to increase the length of the shaft of the sensor 6, and thus the entire reservoir tank, which is undesirable in view of the fact that today's vehicles have an increasing number of parts in the engine room, so that it is required that each part in the engine room be as small in size as possible.
Also, the retainer 9 adds to the number of parts, the number of assembling steps and thus the manufacturing cost of the reservoir tank.
An object of the present invention is to provide a reservoir tank that needs no retainer.